1. Field of the Invention
This invention relates in general to integrated circuits and in particular to memory devices.
2. Description of the Related Art
Memory devices such as e.g. a Random Access Memory (RAM) include sense amplifiers for providing a signal indicative of a value stored in a memory cell of an array coupled to the sense amplifier.
FIG. 1 shows a prior art memory device. Memory device 101 includes a bitcell array 103 having a plurality of memory cells, each for storing a bit of data. The memory cells of bitcell array 103 are each coupled to a pair of differential bit lines BL 105 and *BL 107. Each cell in array 103 is coupled to a word line, which is coupled to row decoder 109. Memory device 101 also includes a column logic 111, sense amplifier circuit 113, latch 115, and output buffer 117. Column logic 111 includes precharge and equalization circuitry, write circuitry, column decode circuitry, and isolation transistors. Latch 115 receives a capacity CLOCK timing signal for enabling latch 115 to sample data from the output of sense amplifier circuit 113. The second amplifier circuit 113 is enabled by a SENSE ENABLE signal.
For memory devices having multiple sense amplifier circuits and latches, providing a clock signal to each latch places a large load on a clock generating circuit, thereby consuming power and degradating the performance of the clock signal. Furthermore, enabling latch 115 with a clock signal requires specific setup and hold time requirements to be maintained between the clock signal and the sense enable signal. Variation in the performance of the memory device may result in the failure to latch the output of the sense amplifier circuit 113. In addition, a latch requires extra circuitry to handle the clock signal. Furthermore, having a latch circuit with a clock input may also introduce unnecessary delay in the operation of a memory device.
What is needed is an improved memory device.
The use of the same reference symbols in different drawings indicates identical items unless otherwise noted.